diff --git a/flang/include/flang/Optimizer/Transforms/Passes.td b/flang/include/flang/Optimizer/Transforms/Passes.td
--- a/flang/include/flang/Optimizer/Transforms/Passes.td
+++ b/flang/include/flang/Optimizer/Transforms/Passes.td
@@ -16,7 +16,7 @@
 
 include "mlir/Pass/PassBase.td"
 
-def AbstractResultOpt : Pass<"abstract-result-opt", "mlir::func::FuncOp"> {
+def AbstractResultOpt : Pass<"abstract-result-opt", "mlir::ModuleOp"> {
   let summary = "Convert fir.array, fir.box and fir.rec function result to "
                 "function argument";
   let description = [{
diff --git a/flang/include/flang/Tools/CLOptions.inc b/flang/include/flang/Tools/CLOptions.inc
--- a/flang/include/flang/Tools/CLOptions.inc
+++ b/flang/include/flang/Tools/CLOptions.inc
@@ -181,7 +181,7 @@
 #if !defined(FLANG_EXCLUDE_CODEGEN)
 inline void createDefaultFIRCodeGenPassPipeline(mlir::PassManager &pm) {
   fir::addBoxedProcedurePass(pm);
-  pm.addNestedPass<mlir::func::FuncOp>(fir::createAbstractResultOptPass());
+  pm.addPass(fir::createAbstractResultOptPass());
   fir::addCodeGenRewritePass(pm);
   fir::addTargetRewritePass(pm);
   fir::addExternalNameConversionPass(pm);
diff --git a/flang/lib/Optimizer/Transforms/AbstractResult.cpp b/flang/lib/Optimizer/Transforms/AbstractResult.cpp
--- a/flang/lib/Optimizer/Transforms/AbstractResult.cpp
+++ b/flang/lib/Optimizer/Transforms/AbstractResult.cpp
@@ -191,40 +191,57 @@
   bool shouldBoxResult;
 };
 
-class AbstractResultOpt : public fir::AbstractResultOptBase<AbstractResultOpt> {
+class FuncOpConversion : public mlir::OpRewritePattern<mlir::func::FuncOp> {
 public:
-  void runOnOperation() override {
-    auto *context = &getContext();
-    auto func = getOperation();
+  using OpRewritePattern::OpRewritePattern;
+  FuncOpConversion(mlir::MLIRContext *context, bool shouldBoxResult)
+      : OpRewritePattern(context), shouldBoxResult{shouldBoxResult} {}
+  mlir::LogicalResult
+  matchAndRewrite(mlir::func::FuncOp func,
+                  mlir::PatternRewriter &rewriter) const override {
+    auto *context = getContext();
     auto loc = func.getLoc();
     mlir::RewritePatternSet patterns(context);
     mlir::ConversionTarget target = *context;
-    const bool shouldBoxResult = passResultAsBox.getValue();
 
     // Convert function type itself if it has an abstract result
     auto funcTy = func.getFunctionType().cast<mlir::FunctionType>();
     if (hasAbstractResult(funcTy)) {
       func.setType(getNewFunctionType(funcTy, shouldBoxResult));
-      unsigned zero = 0;
-      if (!func.empty()) {
-        // Insert new argument
-        mlir::OpBuilder rewriter(context);
-        auto resultType = funcTy.getResult(0);
-        auto argTy = getResultArgumentType(resultType, shouldBoxResult);
-        mlir::Value newArg = func.front().insertArgument(zero, argTy, loc);
-        if (mustEmboxResult(resultType, shouldBoxResult)) {
-          auto bufferType = fir::ReferenceType::get(resultType);
-          rewriter.setInsertionPointToStart(&func.front());
-          newArg = rewriter.create<fir::BoxAddrOp>(loc, bufferType, newArg);
-        }
-        patterns.insert<ReturnOpConversion>(context, newArg);
-        target.addDynamicallyLegalOp<mlir::func::ReturnOp>(
-            [](mlir::func::ReturnOp ret) { return ret.operands().empty(); });
+      if (func.empty()) {
+        // If a function has no body, its conversion is done
+        return mlir::success();
+      }
+      // Insert new argument
+      mlir::OpBuilder rewriter(context);
+      auto resultType = funcTy.getResult(0);
+      auto argTy = getResultArgumentType(resultType, shouldBoxResult);
+      mlir::Value newArg = func.front().insertArgument(0u, argTy, loc);
+      if (mustEmboxResult(resultType, shouldBoxResult)) {
+        auto bufferType = fir::ReferenceType::get(resultType);
+        rewriter.setInsertionPointToStart(&func.front());
+        newArg = rewriter.create<fir::BoxAddrOp>(loc, bufferType, newArg);
       }
+      patterns.insert<ReturnOpConversion>(context, newArg);
+      target.addDynamicallyLegalOp<mlir::func::ReturnOp>(
+          [](mlir::func::ReturnOp ret) { return ret.operands().empty(); });
     }
 
-    if (func.empty())
-      return;
+    return mlir::applyPartialConversion(func, target, std::move(patterns));
+  }
+
+private:
+  bool shouldBoxResult;
+};
+
+class AbstractResultOpt : public fir::AbstractResultOptBase<AbstractResultOpt> {
+public:
+  void runOnOperation() override {
+    auto *context = &getContext();
+    auto module = getOperation();
+    mlir::RewritePatternSet patterns(context);
+    mlir::ConversionTarget target = *context;
+    const bool shouldBoxResult = passResultAsBox.getValue();
 
     // Convert the calls and, if needed,  the ReturnOp in the function body.
     target.addLegalDialect<fir::FIROpsDialect, mlir::arith::ArithmeticDialect,
@@ -250,11 +267,13 @@
     });
 
     patterns.insert<CallOpConversion>(context, shouldBoxResult);
+    patterns.insert<FuncOpConversion>(context, shouldBoxResult);
     patterns.insert<SaveResultOpConversion>(context);
     patterns.insert<AddrOfOpConversion>(context, shouldBoxResult);
-    if (mlir::failed(
-            mlir::applyPartialConversion(func, target, std::move(patterns)))) {
-      mlir::emitError(func.getLoc(), "error in converting abstract results\n");
+    if (mlir::failed(mlir::applyPartialConversion(module, target,
+                                                  std::move(patterns)))) {
+      mlir::emitError(module.getLoc(),
+                      "error in converting abstract results\n");
       signalPassFailure();
     }
   }
diff --git a/flang/test/Driver/mlir-pass-pipeline.f90 b/flang/test/Driver/mlir-pass-pipeline.f90
--- a/flang/test/Driver/mlir-pass-pipeline.f90
+++ b/flang/test/Driver/mlir-pass-pipeline.f90
@@ -25,8 +25,6 @@
 ! CHECK: SimplifyRegionLite
 ! CHECK: CSE
 ! CHECK: BoxedProcedurePass
-
-! CHECK-LABEL: 'func.func' Pipeline
 ! CHECK: AbstractResultOpt
 ! CHECK: CodeGenRewrite
 ! CHECK: TargetRewrite
diff --git a/flang/test/Fir/basic-program.fir b/flang/test/Fir/basic-program.fir
--- a/flang/test/Fir/basic-program.fir
+++ b/flang/test/Fir/basic-program.fir
@@ -34,8 +34,6 @@
 // PASSES: SimplifyRegionLite
 // PASSES: CSE
 // PASSES: BoxedProcedurePass
-
-// PASSES-LABEL: 'func.func' Pipeline
 // PASSES: AbstractResultOpt
 // PASSES: CodeGenRewrite
 // PASSES: TargetRewrite